Aptorchis kuchlingi n. sp. is described from the rectum of the oblong turtle, Chelodina oblonga (Pleurodira: Chelidae), in southwest Western Australia. This digenean is morphologically most similar to Aptorchis pearsoni but can be differentiated from the latter species by: a relatively longer cirrus sac in relation to overall body length, a cirrus sac that reaches the ovary, testes that are situated much closer to the cirrus sac and separated from it only by the seminal receptacle, vitellarium that extends anteriorly beyond the ventral sucker, a relatively wider ventral sucker in relation to oral sucker width, and a pharynx equal in size or larger than the oral sucker. Comparison of approximately 2,400 bases of ribosomal DNA (complete internal transcribed spacer [ITS]1 5.8S ITS2, partial 28S) obtained from all 5 known Aptorchis species also suggests a close relationship of the new species with A. pearsoni and strongly supports the status of A. kuchlingi n. sp. as a new species. This is the fourth species of Aptorchis reported from long-necked turtles (Chelodina) and the first species of the genus reported in C. oblonga.